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exprv4:reference:built_in_methods

Table of Contents



Built-in Methods

Built-in methods are methods provided by Expr value types.

This page covers common value methods, number methods, and string methods.

It does not list methods of built-in objects such as arrays, maps, timers, serial ports, images, crypto objects, GUI controls, or user-defined classes. Those belong to object-specific reference pages.

Method Call Form

A method is called on a value with dot syntax. 

value.method(arguments);

Examples: 

(123).to_string();
'123'.parse_num();
none().is_none();

Parentheses are useful when calling a method on a numeric literal. 

(42).to_hex();

Common Value Methods

These methods can be called on any Expr value.

Method Arguments Returns Meaning
`is_none()` none number True when the value is `none()`.
`is_nan()` none number True when the value is numeric NaN.
`is_num()` none number True when the value is a number, including NaN.
`is_num_notnan()` none number True when the value is a number and not NaN.
`is_num_int()` none number True when the value is an integer numeric value.
`is_string()` none number True when the value is a string.
`is_bool()` none number True when the value can be interpreted as a boolean value.

Examples: 

none().is_none();         // true
nan().is_nan();           // true
(42).is_num_int();        // true
'abc'.is_string();        // true

`is_bool()` is true for finite numbers and for strings that parse as `true`, `false`, `1`, or `0`.

Number Conversion Methods

These methods can be called on number values.

Method Arguments Returns Meaning
`to_bool()` none number Converts the number to a boolean-style numeric value.
`to_int()` none number Converts to signed 32-bit integer.
`to_uint()` none number Converts to unsigned 32-bit integer.
`to_s8()` none number Converts to signed 8-bit integer.
`to_u8()` none number Converts to unsigned 8-bit integer.
`to_s16()` none number Converts to signed 16-bit integer.
`to_u16()` none number Converts to unsigned 16-bit integer.
`to_s32()` none number Converts to signed 32-bit integer.
`to_u32()` none number Converts to unsigned 32-bit integer.
`to_s64()` none number Converts to signed 64-bit integer.
`to_u64()` none number Converts to unsigned 64-bit integer.
`to_string()` none string Converts to decimal string.
`to_string(format)` string string Converts to string using a format string.
`to_hex()` none string Converts to hexadecimal string.
`to_bin()` none string Converts to binary string.
`chr()` none string Converts the low byte of the number to one character.
`chr(count)` number string Repeats that character `count` times.

Examples: 

(255).to_hex();           // FF
(5).to_bin();             // binary text
(65).chr();               // 'A'
(123.456).to_string();

Integer conversion methods round according to Expr numeric conversion rules.

Number Bit Method

`bit()` reads or changes one bit in an integer-like number.

Method Arguments Returns Meaning
`bit(index)` number number Returns true when bit `index` is set.
`bit(index, value)` number, value number Returns a copy of the number with bit `index` set or cleared.

The bit index must be an integer from `0` to `63`.

Examples: 

(5).bit(0);              // true
(5).bit(1);              // false
(4).bit(0, true);        // 5
(5).bit(2, false);       // 1

String Basic Methods

These methods can be called on string values.

Method Arguments Returns Meaning
`length()` none number Number of characters in the string.
`to_string()` none string Returns the string value.
`contains(text)` string number True when the string contains `text`.
`startswith(prefix)` string number True when the string starts with `prefix`.
`endswith(suffix)` string number True when the string ends with `suffix`.
`indexof(text)` string number First position of `text`, or `-1` when not found.
`reverse()` none string Reversed string.

Examples: 

'PlanetCNC'.length();
'PlanetCNC'.contains('CNC');
'abc'.reverse();          // 'cba'

String Slice Methods

Method Arguments Returns Meaning
`substr(start)` number string Substring from `start` to the end.
`substr(start, count)` number, number string Substring starting at `start` with `count` characters.
`slice(start)` number string Alias for `substr(start)`.
`slice(start, count)` number, number string Alias for `substr(start, count)`.
`subspan(start)` number string Substring from `start` to the end.
`subspan(start, end)` number, number string Substring from `start` to `end`.
`span(start)` number string Alias for `subspan(start)`.
`span(start, end)` number, number string Alias for `subspan(start, end)`.
`before(text)` string string Text before the first matching separator.
`after(text)` string string Text after the first matching separator.

Examples: 

'abcdef'.substr(2, 3);    // 'cde'
'key=value'.before('=');  // 'key'
'key=value'.after('=');   // 'value'

String Parsing Methods

Method Arguments Returns Meaning
`parse_num()` none number Parses decimal numeric text.
`parse_hex()` none number Parses hexadecimal text.
`parse_bin()` none number Parses binary text.
`parse_bool()` none number Parses boolean text.

Examples: 

'123'.parse_num();
'FF'.parse_hex();
'1010'.parse_bin();
'true'.parse_bool();

Parsing methods raise a runtime error when the string cannot be parsed by the requested method.

String Formatting Methods

Method Arguments Returns Meaning
`repeat(count)` number string Repeats the string `count` times.
`padleft(pad, length)` string, number string Pads on the left until target length is reached.
`padright(pad, length)` string, number string Pads on the right until target length is reached.
`table()` none string Formats semicolon-separated text as a table.
`table(header)` value string Formats semicolon-separated text as a table, optionally treating the first row as a header.
`ord()` none number Numeric code of the first character, or `0` for an empty string.

Examples: 

'ab'.repeat(3);          // 'ababab'
'7'.padleft('0', 3);     // '007'
'A'.ord();               // 65

String Regex Methods

These methods use regular-expression patterns.

Method Arguments Returns Meaning
`match(pattern)` string number True when the pattern matches.
`find(pattern)` string string First matching text, or empty string when there is no match.
`replace(pattern, replacement)` string, string string Replaces all matches with replacement text.

Examples: 

'abc123'.match('[0-9]+');
'abc123'.find('[0-9]+');
'abc123'.replace('[0-9]+', '');

Invalid regular-expression patterns raise a runtime error.

String Trim and Case Methods

Method Arguments Returns Meaning
`trim()` none string Removes whitespace from both ends.
`trimleft()` none string Removes whitespace from the start.
`trimright()` none string Removes whitespace from the end.
`upper()` none string Converts to uppercase.
`lower()` none string Converts to lowercase.

Examples: 

'  abc  '.trim();
'abc'.upper();
'ABC'.lower();

Not Covered Here

Object methods are not listed on this page.

Examples of object methods that belong to object-specific pages: 

array(1, 2, 3).size();
map().set('x', 1);
window().show();
serial().open('COM1');

Those methods are part of the object returned by the constructor, not part of the built-in value-method set.

Common Pitfalls

Calling Number Methods on Literals Without Parentheses

Use parentheses when the target is a numeric literal. 

(123).to_string();

Looking For Old Global Conversion Functions

Conversions are methods on values. 

value.to_string();
text.parse_num();

Do not use old global conversion-function style.

Confusing Object Methods With Value Methods

`array().size()` is a method, but it is an array object method. It is not documented on this page.

Previous: Methods and properties

Next: Common Value Methods

exprv4/reference/built_in_methods.txt · Last modified: by andrej

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